lib: initialize instance members in class constructors

Since V8 snapshot does not currently support instance member
initialization, initialize them in ordianry class constructors
for now so that these classes can be included in the snapshot.
This may be reverted once
https://bugs.chromium.org/p/v8/issues/detail?id=10704
is fixed and backported.

PR-URL: https://github.com/nodejs/node/pull/32984


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>